The invention relates to an expansion anchor. Such an expansion anchor is designed with a bolt as a first element and with an expansion sleeve, which at least partially surrounds the bolt, as a second element, wherein the bolt has an expansion region for spreading apart the expansion sleeve, wherein one of the two elements, particularly on an external peripheral surface or internal peripheral surface, has a groove running in the longitudinal direction of the expansion anchor and the other element has a projection, which engages at least sectionally in the groove.
Expansion anchors are known from DE 101 08 844 A1, for example. They are used in a borehole in a substrate, e.g., in a wall or a ceiling of a construction unit. By pulling the expansion region of the bolt into the expansion sleeve, the latter is radially widened and the expansion anchor is anchored in the substrate.
EP 0 515 916 A2 and DE 22 56 822 A1 describe expansion anchors, in which an anti-rotation means of the expansion sleeve on the bolt is prevented by a groove guide.
The object of the invention is to provide an expansion anchor, which achieves particularly good load values, while having low production costs and high reliability.
The expansion anchor according to the invention is characterized in that the groove has a narrowing that inhibits an axial movement of the expansion sleeve relative to the bolt.
According to the invention, the groove has a narrowing that inhibits an axial movement of the projection relative to the groove, and thus an axial movement of the expansion sleeve relative to the bolt, preferably an axial movement of the expansion sleeve relative to the bolt into the expansion region.
According to the invention, it is thus provided that the cross-section of the groove along the bolt varies, so that the projection engaging into the groove rubs against the groove at varying levels of intensity, depending on the position of the expansion sleeve relative to the bolt, which in turn results in varying forces being required, depending on the position of the expansion sleeve relative to the bolt, to displace the expansion sleeve on the bolt. According to the invention, and in a particularly simple and cost-effective manner, an additional parameter is provided with which one can control the anchoring process of the anchor. This in turn allows one to resolve conflicts that may exist under certain circumstances in conventional expansion anchors. For example, in regard to conventional anchors, it may be desirable to have a relatively stiff design of the sleeve on the one hand, e.g., to counteract the possibility of a premature complete pull-through of the bolt through the sleeve when the anchor is set; however, simultaneously, a relatively malleable design of the sleeve may be desired so that it can adapt particularly well to the substrate for example, and thereby offer particularly good load transfer values. According to the invention, the pull-through behavior can now also be controlled by means of the narrowing of the groove, so that the sleeve can be selected to be malleable in regard to load transfer values, without having to hereby consider the pull-through behavior to a significant degree. In this way, a particularly reliable anchor can be obtained according to the invention.
The narrowing exists for practical purposes at least in the peripheral direction of the bolt and/or the expansion sleeve, i.e., seen in the peripheral direction, the groove at the narrowing is preferably narrower than the width of the projection. Preferably, the groove outside the narrowing is cross-sectionally greater than the projection in such a manner that the projection there can move in an essentially non-frictional manner in the groove. In particular, the groove outside of the narrowing, as seen in the peripheral direction of the bolt and/or the expansion sleeve, may be wider than the projection. This can also have production-related advantages. In particular, in this case the sleeve may be rolled in an especially load-free manner, and thus in an especially simple manner, on the bolt.
The bolt may have a neck region for receiving the expansion sleeve prior to expansion, in which the bolt has preferably, at least sectionally, an at least almost constant cross-section in the longitudinal direction. In the expansion region, the bolt widens towards its tip, i.e., as the distance increases from the neck region. The groove and/or the projection run preferably parallel to the longitudinal axis of the bolt and/or expansion anchor. To the extent that the radial direction and the longitudinal direction are mentioned here, this shall refer in particular to the longitudinal axis of the bolt and/or the anchor, which may be in particular the symmetrical and/or central axis of the bolt and the anchor, respectively.
The expansion sleeve and/or the bolt consist preferably of a metal material. Preferably, the bolt has on its end region opposite the expansion region exterior threads for a nut. In particular, on the bolt, there may be designed a stop, for example, an annular shoulder, which limits a displacement of the sleeve away from the expansion region. However, the expansion sleeve, which may also be designed in a multi-part manner, may also extend to the exterior threads of the bolt. The expansion region is provided according to the invention for spreading out the expansion sleeve, i.e., for the radial widening of the expansion sleeve.
The projection engaging into the groove may also form an anti-rotation means, which inhibits a rotation of the expansion sleeve relative to the bolt about the longitudinal axis of the bolt. Fundamentally, the projection could have discontinuities. However, the projection is preferably continuous.
It is especially preferred that the groove arranged on the bolt, or the projection arranged on the bolt, runs at least partially outside of the expansion region. This design may take into account among other things that the tensile forces of the set expansion anchor are introduced primarily in the expansion region in the bolt. By the groove or the projection running at least partially, preferably entirely, outside the expansion region, one avoids impairing the force transmission. Preferably, the groove, or the projection, on the bolt runs at least sectionally in the neck region, i.e., especially in the region between the expansion region and the stop for the expansion sleeve.
Furthermore, it is preferred that the projection is arranged on the bolt and the groove is arranged on the expansion sleeve. This may be especially advantageous in a production-related manner. For example, the groove may be rolled in. The projection may be formed during a rolling or compressing process.
Alternatively, it may be provided that the projection is arranged on the expansion sleeve and the groove is arranged on the bolt. In this context, it may be especially advantageous that the wall thickness of the expansion sleeve is increased locally by the projection. On the projection, a particularly large expansion can hereby be achieved, without the neck region of the bolt, in which the projection is arranged prior to expansion, being significantly weakened. A local wall thickness increase may refer especially to the wall thickness being larger at the projection than in its periphery.
It may also be provided that the expansion anchor has a plurality of grooves running in the longitudinal, direction of the expansion anchor and a plurality of respective corresponding projections, wherein at least part of the grooves each have a narrowing, which inhibits an axial movement of the corresponding projection and thus an axial movement of the expansion sleeve relative to the bolt, particularly an axial movement of the expansion sleeve relative to the bolt into the expansion region. In addition, all grooves may have such a narrowing. For example, all grooves may be provided on one of the elements and all projections may be provided on the other element. However, a mixed arrangement may also be provided, in which one of the elements has part of the grooves and one has part of the projections.
Depending on the desired force progression, it may be advantageous that the narrowing is provided at one end of the groove or in a middle region of the groove.
Preferably, the projection is a cross-piece, which extends in the longitudinal direction of the expansion anchor, and runs in particular parallel to the longitudinal direction of the expansion anchor. The displacement behavior of the expansion sleeve can thereby be controlled in a more exact manner.
The invention is subsequently explained in further detail by means of preferred embodiments, which are schematically illustrated in the enclosed drawings, wherein individual features of the subsequently depicted embodiments may be executed within the scope of the invention basically in an individual manner or in any combination.